JPS6019115A - Surface treatment of connection part of optical fiber - Google Patents

Abstract

PURPOSE:To make a processing work easy by treating the surface of a fiber connection part after connection by welding with a premixed combustion flame of a fuel gas, an oxidizing gas, and a gas containing fluorine and making the processing work possible even if conditions of a work field or the like are bad. CONSTITUTION:A bomb 17 (combustion gas), a bomb 18 (oxidizing gas), and a bomb 19 (gas containing fluorine) are connected to a mixer 10 in the center, and degrees of opening of cocks 14, 15, and 16 are adjusted to set gas flow rates of individual bombs to prescribed quantities while confirming gauges 11, 12, and 13. The connection part between fibers 5 and 5' is arranged on a flame 21 formed by firing a gas burner 20 and is subjected to the surface treatment, and flaws on surfaces of fibers 5 and 5' are eliminated by etching due to gaseous fluorine; and if necessary, the temperature of the flame 21 is raised to about 2,000 deg.C to evaporate surface layer parts of fibers 5 and 5', and flaws are eliminated by fire polishing.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a surface treatment method for a fusion-spliced optical fiber connection part suitable for, for example, communication optical fibers.

(Prior art) In general, the number and depth of minute scratches (cracks) that occur on the fiber surface are considered to be major factors that reduce the mechanical strength of optical fibers. Immediately after drawing, a primary coating of silicone resin or the like is applied to protect the fiber surface.

However, in fusion splicing of optical fibers using the arc discharge method or the micro gas torch method, the jacket including the primary coating covering the fiber is removed and the fiber is spliced with the fiber exposed. There is a problem in that countless scratches are created on the surface of the fiber when it is set in a device, or the existing scratches are enlarged, which reduces the mechanical strength of the optical fiber after the fiber is connected. Furthermore, when fusion splicing is performed, thermal strain due to the fusion heat remains in the fiber, and this strain also causes mechanical strength deterioration.

Therefore, as a method for removing scratches on the fiber surface, a method has already been proposed in which the surface of the fiber is treated with a mixed solution of hydrofluoric acid and sulfuric acid. However, this method requires the handling of strong acids, which makes the work cumbersome, and is therefore unsuitable for implementation, particularly at work sites.

(Objective of the invention) Utilizing the etching effect of fluorine on the fiber surface,
Moreover, the present invention provides a surface treatment method that is easy to work with and can be carried out even when the conditions at a work site are not very good.

(Structure of the Invention) A method for surface treatment of an optical fiber spliced portion is characterized in that a fiber spliced portion after fusion splicing is surface treated with a mixed combustion flame of a fuel gas, an oxidizing gas, and a fluorine-containing gas.

(Embodiment) As shown in FIG. 1, an optical fiber cable 1 generally has a core 2 made of high-purity quartz glass at the center, and a cladding made of quartz glass having a lower refractive index than the core 2 around the core 2. A layer 3 is formed, and a support layer 4 made of quartz glass is formed around it, and these cores 2,
A fiber 5 is formed by the cladding layer 3 and the support layer 4 (the support layer 4 may be omitted).

The area around the fiber 5 is made of resin (for example, made of silicone resin).
A precoat 6 is formed on the outer periphery of the precoat 6, and a thick jacket body 7 made of resin (for example, made of nylon) is formed as a protective coating layer, and the precoat 6 and the jacket body 7 form a jacket 8. .

When performing optical fiber fusion splicing, as shown in FIG. The end surfaces of the fibers 5 and 5 are abutted against each other, and the abutted fibers 5 and the ends of the dazzles are fusion spliced using an arc fusion splicing method or the like while accurately aligning each layer of the fibers 5.5.

In the fusion spliced portion of the optical fiber 5.5' thus obtained, in addition to scratches during the production of the fiber 5.5', there are scratches on the surface layer where newly generated acid has grown due to the subsequent operation.

a) Jacket 8.82 removal work.

b) Cutting the end face of the 5.5” fiber at right angles.

C) Loading the fiber 5.5'' into a holding device (not shown) for fusion splicing.

Next, by the surface treatment method according to the present invention, the fiber 5.
5' surface treatment is performed. FIG. 3 is a schematic diagram of the surface treatment apparatus. Each central mixer 10 has a gauge 11.
．． 12.13 and cylinders 17.18.19 are connected via cocks 14.15.16. The cylinder 17 is filled with combustion gas (for example, hydrogen, butane, LPG, etc.), and the cylinder 18 is filled with an oxidizing gas (for example, oxygen, compressed air, etc.). Further, the cylinder 19 is filled with a fluorine-containing gas (for example, SFa, etc.). Each cylinder 1
The gas flow rate at 7.18.19 is set to a predetermined amount by adjusting the opening degree of the cock 14.15.16 while checking with the gauge 11.12.13. The mixed gas mixed in the mixer 10 is ejected from the gas burner 20 and ignited.

A flame 21 is formed at the tip of the gas burner 20 by ignition, and the fiber 5 between the cables 1 and 19 is placed on the flame 21.
．． A 5' connection is placed. Then, the burner 20 is moved in one direction along the length of the fiber 5.5°, or the cable i,
By reciprocating i' in the longitudinal direction, the surface of the exposed fiber 5.5' is treated.

When SFa is used as the fluorine-containing gas, Sv
S decomposes when the temperature reaches several hundred degrees, and fluorine etches the surface layer of the fibers 5 and 5', thereby removing the defects on the surfaces of the fibers 5 and 5'. The residual thermal strain caused during fusion splicing causes the fiber 5.5' to be exposed to the flame 2.
1 and removed at the same time by raising the temperature.

If necessary, the temperature of the flame 21 is raised to about 2000 degrees to bring it to about the melting temperature of the fiber 5.5 degrees, and the fire borizing effect is applied to remove scratches by evaporating the surface layer of the fibers 5 and 5. can be obtained at the same time.

Next is Flavor 5.52. There are no scratches on the surface layer (cable l)
, 1'' is housed in, for example, a box-shaped splice piece 22 as shown by phantom lines in FIG. 2, and is fixed with adhesive or the like to further provide protection and reinforcement.

(Effects of the Invention) (Since a fluorine-containing gas is used, the fluorine etching action can be utilized, and the work is easy, even in places where conditions are not very good, such as a work site.

(b) By utilizing the high temperature of the flame 21, it is possible to eliminate thermal strain remaining in the fiber 5.5° at the same time as fluorine etching.

(C) Fluorine etching and fire polishing can be performed simultaneously by raising the temperature of the flame 21 to about the melting temperature of the fiber 5.5.
It also becomes possible to shorten the surface treatment time of 5'.

(Another Embodiment) The burner 20 is not only moved in the longitudinal direction of the fiber 5.5", but also rotated around the fiber 5.5" to perform surface treatment from the side and above. Ba,
More uniform processing can be performed. If the cable 1.19 is rotatable, the cable 1.11 may be rotated over the burner 20.

[Brief explanation of the drawing]

Fig. 1 is a vertical sectional front view of a typical optical fiber cable, Fig. 2 is a side view of the vicinity of the fusion splice, and Fig. 3 is a schematic diagram of a surface treatment device for carrying out the surface treatment method according to the present invention. be. , 5.5-...Fiber, 21...Flame patent applicant Tadashi Omori, patent attorney for Dainichi Nippon Electric Cable Co., Ltd.

Claims (1)

[Claims] 1. A method for surface treatment of an optical fiber spliced portion, which comprises surface-treating the fiber spliced portion after fusion splicing with a mixed combustion flame of a fuel gas, an oxidizing gas, and a fluorine-containing gas.